1. Field of the Invention
The present invention relates to an optical connector adapted to be used as an optical signal input terminal for receiving an optical signal or an optical signal output terminal for outputting an optical signal, and more particularly, to a miniaturized optical connector adapted to be suitably used in any one of many kinds of audio visual apparatuses, personal computers, mobile communication apparatuses, etc., by mounting the optical connector thereto as an optical signal input terminal or an optical signal output terminal.
2. Description of the Related Art
Miniaturized audio visual apparatuses such as a DVD (Digital Versatile Disk) player/recorder, MD (Mini-Disk) player/recorder, CD (Compact Disk) player/recorder, etc., portable audio apparatuses such as an MD portable player/recorder, CD portable player/recorder, memory type audio apparatus (audio apparatus using a memory card), etc., personal computers, mobile communication apparatuses such as a mobile phone, pocket or portable telephone, etc., or the like have been miniaturized more and more in their external configurations or shapes and dimensions or sizes, and accordingly, an input terminal and/or output terminal built in or mounted to these electronic apparatuses have been also miniaturized. Particularly, in recent years, with the advance of optical technology, there have been appeared many kinds of electronic apparatuses and appliances, each having an optical connector mounted thereto as an optical signal input terminal for receiving an optical or light digital signal or an optical signal output terminal for outputting an optical or light digital signal.
An optical connector mounted to any one of various electronic apparatuses and appliances has a light receiving element or light emitting element housed in the connector body thereof, and for instance, one of two optical plugs mounted to an optical cable (for example, optical fiber) at opposed ends thereof respectively, that transmits an optical or light digital signal is directly plugged in the optical connector, so that an optical digital signal is transmitted from the optical cable to the optical connector or from the optical connector to the optical cable.
In Japan, there have been generally used as optical connectors for many kinds of audio visual apparatuses an optical plug having its plug portion of 3.5 mm in outside diameter and an optical receptacle or jack configured such that an optical plug of this size can be plugged therein, and an optical plug having its plug portion of 2.5 mm in outside diameter and an optical receptacle or jack configured such that an optical plug of this size can be plugged therein. However, as stated above, with the miniaturization of various kinds of electronic apparatuses and appliances, there have been proposed optical plugs each having its plug portion of 2 mm or smaller than 2 mm in outside diameter, and the necessity of providing optical receptacles or jacks each being configured such that corresponding one of such optical plugs can be plugged therein is increased.
The assignee of the present application has been proposed an ultra-miniaturized optical receptacle or jack (hereinafter, referred to as optical connector) configured such that an optical plug having its plug portion of 2.5 mm in outside diameter can be plugged therein. At first, such ultra-miniaturized optical connector proposed by the assignee of the present application will be described in detail with reference to FIGS. 6 to 9.
The optical connector comprises a connector body 11 of generally rectangular shape in section and made of an insulation material, and a sleeve 12 formed integrally with the connector body 11 at the front end thereof and projecting forward from the connector body 11. An optical element accommodation section 15 is formed in the connector body 11 at the rear end portion thereof. As is clear from FIG. 7, a plug-in hole 13 configured such that an optical plug having its plug portion of 2.5 mm in outside diameter can be plugged therein is formed through the sleeve 12 and is in communication with a plug guide hole 11A in substantially coaxial relation therebetween, the plug guide hole 11A being formed through the connector body 11 in the longitudinal direction thereof and extending from the front end surface of the body 11 to the optical element accommodation section 15.
The optical element 14 is housed in the optical element accommodation section 15. The optical element 14 is arranged such that in case the optical connector is an optical signal input terminal, the light receiving surface of the optical element 14 is faced to the opening at the rear end of the plug guide hole 11A and in case the optical connector is an optical signal output terminal, the light emitting surface of the optical element 14 is faced to the opening at the rear end of the plug guide hole 11A. In such cases, as shown in FIG. 8, the optical element 14 is arranged such that the optical axis P thereof and the axis of the plug guide hole 11A align or accord with each other. As a result, an optical plug plugged in the plug-in hole 13 and the optical plane of the optical element 14 are optically coupled with each other with a low optical loss, and hence it is possible to transmit an optical digital signal with high efficiency from an optical cable that has been connected to the optical plug to the optical element 14 or from the optical element 14 to the optical cable.
Further, in the illustrated example, the optical element 14 is an element of the type that four terminals 16 thereof are led out backward in parallel with one another from the bottom of the package of the optical element 14. Accordingly, the optical element accommodation section 15 has its bottom opened as shown in FIG. 9, and in the top wall of the optical element accommodation section 15 is formed a slit-like opening that is elongate in its width direction as shown in FIG. 6, the slit-like opening serving to position the top of the package of the optical element 14. As a result, the optical element 14 is inserted into the optical element accommodation section 15 from the bottom side of the connector body 11, and is mounted in place therein by fitting the top of the package in the slit-like opening and positioning the package in place.
Meanwhile, a pair of ground terminals 17 are mounted to the connector body 11 in such manner that they project outwardly respectively from the opposed side surfaces of the connector body 11 at the forward locations thereof to the optical element accommodation section 15. In addition, as shown in FIGS. 7 and 9, the pair of ground terminals 17 have resilient plug holding pieces 19 integrally formed therewith, respectively, and these plug holding pieces 19 are inserted into recesses 18 respectively that are formed at opposite sides of the plug guide hole 11A of the connector body 11 in such manner that they are opposed to each other. These recesses 18 are in communication with the plug guide hole 11A, and when the pair of plug holding pieces 19 are inserted into the corresponding recesses 18 respectively, as shown in FIG. 7, bent portions of the pair of plug holding pieces 19 formed in the vicinity of the forward ends thereof protrude in the plug guide hole 11A in such manner that the bent portions are diametrically opposed to each other, and therefore, the plug guide hole 11A becomes narrower at that portion. Accordingly, when an optical plug having its plug portion of 2.5 mm in outside diameter is inserted into the plug-in hole 13, the tip portion of the optical plug advances between the bent portions of the pair of plug holding pieces 19 so that the bent portions are broadened outwardly. The instance that the maximum diameter portion of the tip portion pass beyond the bent portions, the end surface of the larger diameter portion of the optical plug abuts against the front end surface of the sleeve 12, and hence the optical plug stops advancing. Consequently, a portion immediately after the maximum diameter portion of the tip portion is pressed by and sandwiched or nipped between the bent portions by the resilient forces thereof. Thus, the optical plug is held in the state that it faces exactly the optical plane of the optical element 14.
The optical connector shown in FIGS. 6 to 9 is an optical connector configured such that the length (the depth) L1 extending from the front end of the plug-in hole 13 (the front end surface of the sleeve 12) to the rear end surface of the connector body 11 is set to about 10 mm and the width L2 of the connector body 11 is set to about 7 mm (see FIG. 6), and corresponding to, as stated above, an optical plug having its plug portion of 2.5 mm in outside diameter.
As discussed above, the optical connector proposed by the assignee of the present application has the optical element 14 accommodated in the connector body 11 made of an insulation resin, and the periphery of the optical element 14 is surrounded by the walls of insulation resin constituting the connector body 11. In order to strengthen or reinforce the resin wall to some extent, it is necessary to make the thickness of the resin wall comparatively thicker. For this reason, there is needed a space on the periphery of the optical element 14, the space corresponding to the insulation resin wall of the connector body 11. Therefore, the area in cross-section of the connector body 11 (the area in section thereof in the direction orthogonal to the plug-in hole 13) is larger than that of the optical element 14 by the thickness of the resin wall.
FIG. 10 shows the relation between the areas in cross-section of the connector body 11 and the optical element 14 stated above. As described above, the optical element 14 is housed in the optical element accommodation section 15 formed in the backward end portion of the connector body 11. For this reason, the thickness T of the insulation resin wall of the connector body 11 on the top surface, opposed side surfaces and rear surface of the optical element 14 is added to dimensions of the height, width and depth of the optical element 14, and hence there is a disadvantage that the external shape and size or dimension of the connector body 11 are increased by the thickness T of the insulation resin wall. As shown in FIG. 10, assuming that the dimension in the width direction of the optical element 14 is W and the height of the optical element 14 is H, the dimension A in the width direction of and the height B of the connector body 11 are expressed by the following equations.
Axe2x89xa7W+2T
Bxe2x89xa7H+T
As to the height B of the connector body 11, it is possible that the height B is reduced to a size substantially equal to the height H of the optical element 14 by forming, in the top wall of the optical element accommodation section 15, a slit-like opening that is elongate in the width direction thereof and serves to position the top of the package of the optical element 14, as described above with reference to FIG. 6. However, it is impossible to reduce the thickness of the insulation resin wall of the connector body 11 existing on the opposed side surfaces and the rear surface of the optical element 14. Thus, it is difficult to further miniaturize the optical connector.
In case of using a resin as the insulation wall of the connector body 11, unless the thickness T of the insulation resin wall of the connector body 11 is set to 1 mm to 1.5 mm, the insulation resin wall cannot have an appropriate strength. Accordingly, in case the size A of the connector body 11 in the width direction thereof is set to 7 mm, the thickness of the insulation resin wall becomes 2 mm to 3 mm, and so, the proportion of the insulation resin wall to the width size A of the connector body 11 comes to 29% to 43%. In this manner, the proportion of the insulation resin wall to the width of the connector body 11 is very high, which results in a serious cause that the optical connector is hindered in its further miniaturization.
An object of the present invention is to provide an ultra-miniaturized optical connector in which the external shape and size of an element holder for accommodating an optical element therein can be reduced up to substantially the same as those of the optical element.
Another object of the present invention is to provide an ultra-miniaturized optical connector in which the area in cross-section of the connector body can be reduced up to substantially the same as that of the optical element.
In order to accomplish the foregoing objects, in an aspect of the present invention, there is provided an optical connector which comprises: a generally square-shaped insulation body; a plug guide hole passing through the insulation body; plug holding members provided in the insulation body, and resiliently sandwiching and holding an optical plug inserted into the plug guide hole to add to the optical plug a force for preventing the optical plug from coming off; an optical element to be mounted to the rear end surface of the insulation body; an element holder to be attached to the rear end of the insulation body, that comprises a top plate, opposed side plates and a rear plate covering the top surface, the opposed side surfaces and the rear surface of the optical element respectively when the optical element is mounted in the element holder, a size between the inner surfaces of the opposed side plates being set to a value substantially equal to the maximum value in the tolerance of the corresponding external size of the optical element, the element folder being made of an electrically conductive sheet metal; a pair of engagement pieces extending forward respectively from the opposed side plates of the element holder in such manner that each engagement piece and the corresponding side plate are flush with each other, the pair of engagement pieces being engaged with engaging portions formed on the opposed side surfaces of the insulation body respectively to attach the element holder to the rear end of the insulation body; a plurality of protuberances formed on and projecting from the rear end surface of the insulation body, the plurality of protuberances engaging with the forward portion of the optical element to maintain the mounting position of the optical element at a predetermined position; and biasing force applying means provided on the rear plate of the element holder and applying to the optical element a resilient biasing force that acts, when the element holder is attached to the rear end of the insulation body, to forcedly push the front surface of the optical element mounted in the element holder against the rear end surface of the insulation body.
In a preferred embodiment, tongues for resiliently sandwiching and holding the optical element to prevent the optical element from coming off when the optical element is mounted in the element holder, are formed by cutting a portion of each side plate of the element holder and bending the cut portion inward.
The biasing force applying means is constituted by two slits formed in the rear plate of the element holder in parallel with each other in the height direction thereof at a very small interval therebetween; a strip-like portion between the slits; and a curved portion formed by pushing the strip-like portion inward to protrude inward, and two of the biasing force applying means are provided on the rear plate of the element holder at a predetermined interval. Only one biasing force applying means may be provided on the rear plate of the element holder.
The length of the rear plate of the element holder is set to a size shorter than the length of each side plate of the element holder, and the element holder is configured such that when the optical element is mounted in the element holder, terminals of the optical element are led out toward the outside through an opening portion formed under the lower end of the rear plate.
In addition, each of the opposed side plates of the element holder has a ground terminal formed integrally with the corresponding side plate at the lower end thereof and projecting outwardly from the lower end thereof. Only one of the opposed side plates of the element holder may have a ground terminal formed integrally with the side plate at the lower end thereof and projecting outwardly.
In another preferred embodiment, a slit for receiving the top portion of the top surface of the optical element when the optical element is mounted in the element holder, is formed in the top plate of the element holder in the width direction of the top plate.
In accordance with the construction of the present invention, the optical connector is arranged such that an optical element is accommodated in the element holder made by use of a sheet metal, and that the element holder is engaged with and attached to the rear end of the insulation body. Since the sheet metal has its strength higher than that of a resin, the thickness of the sheet metal constituting the element holder can be considerably decreased. As a result, it is possible to reduce the size of the external form of the element holder boundlessly down to that of the external form of the optical element.
In this manner, since the size of the external form of the element holder can be boundlessly reduced down to that of the external form of the optical element, the size in the width direction of the external form of the insulation body to which the element holder is attached can be boundlessly reduced down to that of the external form of the optical element. Accordingly, the whole external form or shape of the optical connector can be ultra-miniaturized.